JavaFX WebEngine 生成 StringIndexOutOfBoundsException，出了什么问题？

Question

我有一个使用 JavaFX 的小实验项目，其中有一个按钮和一个 WebView。按下按钮时，将加载网站:

package sample;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.web.WebView;

public class Controller {
    @FXML private Button theButton;
    @FXML private WebView theWebView;


    @FXML
    protected void loadWebSite(ActionEvent event) {
        theWebView.getEngine().load("https://dashman.tech");
    }
}

发生这种情况时，我会收到以下错误:

java.lang.StringIndexOutOfBoundsException: String index out of range: 4
    at java.lang.String.substring(String.java:1963)
    at com.sun.javafx.webkit.prism.WCGraphicsPrismContext.drawString(WCGraphicsPrismContext.java:960)
    at com.sun.webkit.graphics.GraphicsDecoder.decode(GraphicsDecoder.java:290)
    at com.sun.webkit.graphics.WCRenderQueue.decode(WCRenderQueue.java:91)
    at com.sun.webkit.graphics.WCRenderQueue.decode(WCRenderQueue.java:102)
    at com.sun.webkit.graphics.WCImage.flushRQ(WCImage.java:52)
    at com.sun.javafx.webkit.prism.RTImage.lambda$getPixelBuffer$77(RTImage.java:163)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
    at com.sun.javafx.tk.RenderJob.run(RenderJob.java:58)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:125)
    at java.lang.Thread.run(Thread.java:745)
java.lang.StringIndexOutOfBoundsException: String index out of range: 7
    at java.lang.String.substring(String.java:1963)
    at com.sun.javafx.webkit.prism.WCGraphicsPrismContext.drawString(WCGraphicsPrismContext.java:960)
    at com.sun.webkit.graphics.GraphicsDecoder.decode(GraphicsDecoder.java:290)
    at com.sun.webkit.graphics.WCRenderQueue.decode(WCRenderQueue.java:91)
    at com.sun.webkit.graphics.WCRenderQueue.decode(WCRenderQueue.java:102)
    at com.sun.webkit.graphics.WCImage.flushRQ(WCImage.java:52)
    at com.sun.javafx.webkit.prism.RTImage.lambda$getPixelBuffer$77(RTImage.java:163)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
    at com.sun.javafx.tk.RenderJob.run(RenderJob.java:58)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:125)
    at java.lang.Thread.run(Thread.java:745)
java.lang.StringIndexOutOfBoundsException: String index out of range: 6
    at java.lang.String.substring(String.java:1963)
    at com.sun.javafx.webkit.prism.WCGraphicsPrismContext.drawString(WCGraphicsPrismContext.java:960)
    at com.sun.webkit.graphics.GraphicsDecoder.decode(GraphicsDecoder.java:290)
    at com.sun.webkit.graphics.WCRenderQueue.decode(WCRenderQueue.java:91)
    at com.sun.webkit.graphics.WCRenderQueue.decode(WCRenderQueue.java:102)
    at com.sun.webkit.graphics.WCImage.flushRQ(WCImage.java:52)
    at com.sun.javafx.webkit.prism.RTImage.lambda$getPixelBuffer$77(RTImage.java:163)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
    at com.sun.javafx.tk.RenderJob.run(RenderJob.java:58)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:125)
    at java.lang.Thread.run(Thread.java:745)

有什么想法吗？我该如何预防？该网站似乎加载良好。其他网站不会生成这些错误。

Answer 1

当我在 Mac OSX 上使用 jdk1.8.0_131 进行测试时，我得到了一个略有不同的错误，其中使用了堆栈上的 native 方法的不同堆栈:

Exception in thread "JavaFX Application Thread" java.lang.StringIndexOutOfBoundsException: String index out of range: 4
    at java.lang.String.substring(String.java:1963)
    at com.sun.javafx.webkit.prism.WCFontImpl.getGlyphsAndAdvances(WCFontImpl.java:120)
    at com.sun.webkit.network.URLLoader.twkDidReceiveData(Native Method)
    at com.sun.webkit.network.URLLoader.notifyDidReceiveData(URLLoader.java:844)
    at com.sun.webkit.network.URLLoader.lambda$didReceiveData$102(URLLoader.java:819)
    at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)

当我将com.sun.javafx.webkit.prism.WCFontImpl的日志记录级别设置为全部时，我得到以下信息:

c.sun.javafx.webkit.prism.WCFontImpl - str='ð' (length=2), from=0, to=4, rtl=false
c.sun.javafx.webkit.prism.WCFontImpl - str='ð©' (length=4), from=0, to=7, rtl=false
c.sun.javafx.webkit.prism.WCFontImpl - str='ð' (length=3), from=0, to=6, rtl=false

当我查看字符串时，日志消息中的长度似乎是正确的字符数，但 from 和 to 的参数似乎不采用考虑到字符串包含多字节字符。这些错误的值用于子字符串调用，然后导致异常。我无法找出哪种字体在这里造成麻烦。

所以我认为，该网站加载了一些已损坏或不正确的字体。浏览器引擎会忽略这些错误，尽管会转储堆栈跟踪，这就是页面仍然可以工作的原因 - 也许没有以所需的字体显示某些内容。

为什么你有不同的堆栈跟踪？我不确定，这可能是因为您使用不同的操作系统或不同的 Java 版本？

而且我认为您无法阻止这种情况，除非您对该网站负责并检查所使用的字体。